An analog-to-digital converter is widely used in various electronic components to convert continuous analog signals into discrete digital signals, such as converting analog signals of various sensors into digital output signals. However, an analog-to-digital converter has a problem in that an offset caused during analog signal sampling and a quantization error caused during digital signal conversion will affect the accuracy of the analog-to-digital converter. In addition, when an input signal or a related circuit is disturbed, the ability to resist noise also influences the performance of an analog-to-digital converter.
Taiwanese Patent No. I330,467 discloses an analog digital conversion device applied to orthogonal frequency division multiplexing and ultra-wideband, wherein a frequency difference is complemented or reduced, and a signal is modulated to increase ratio of signal to quantization noise (SQNR) by about 5 dB.
U.S. Pat. No. 9,455,733 discloses an analog-to-digital converter with an adjustable sampling frequency wherein pseudo-noise sequence is used for modulation. However, the above two modulations need demodulation circuits.
Taiwanese Patent No. I404,345 discloses a sigma-delta modulator with a controllable output rate, wherein the output rate of the sigma-delta modulator is controlled according to an amplitude of an input signal, and a period of a first clock is multiplied by an integer as an adjusted operating frequency. However, resistance to noise is not enhanced.